1. Field of the Invention
This invention relates to an inductance element, and more particularly it pertains to such an inductance element adapted to be used as power transformer or coil for a switching power supply device.
2. Description of the Prior Art
Recently, a switching power supply device has been extensively used with a wide variety of electric equipment and implements. To cope with miniaturization of electric equipment and implements, it has been demanded that the power supply device be made lighter and thinner. Capacitors and coils used in a switching power supply device may be smaller in size for a higher switching frequency, and thus there is a tendency that an extremely high switching frequency is used.
To render coils and transformers operable at a high frequency, it is necessary to use a core material adapted for such a high-frequency application. A bulky core such as ferrite core or the like has conventionally been used with a transformer or coil for a switching power supply device. However, because of the fact that variations in magnetization of the core which occur when the transformer or coil is energized with a driving current, are caused through movement of magnetic domain walls, the core fails to follow a switching frequency as high as about 200 KHz, and thus if it is attempted to effect switching operation at a rate higher than that, power loss is greatly increased so that the transformer or coil using such a core turns out to be inoperative.
SUMMARY OF THE INVENTION
The present invention has been made with a view to eliminating the aforementioned drawbacks of the prior art. It is a primary object of the present invention to provide an inductance element having an improved high-frequency characteristic.
Briefly, according to present invention, there is provided an inductance element which comprises at least one annular core formed by a magnetic foil belt wound in a volute form and comprising magnetic thin films deposited on a tape-like thin plate, and at least one wire wound on said core. The magnetic thin films are provided with an axis of easy magnetization direction in the direction of width of the magnetic foil belt. Alternatively, the core may be formed by plural pieces of magnetic foil belt comprising magnetic thin films deposited on a tape-like thin plate, said plural pieces of magnetic foil belt being insulated from each other and provided in a laminated form. Furthermore, at least one closed magnetic circuit is established by means of one or more cores.
Other objects, features and advantages of the present invention will become apparent from the ensuing description taken in conjunction with the accompanying drawings.